1. Field of the Invention
The present invention relates to temperature control systems. In particular the invention relates to systems which provide improved temperature control leading to faster and more accurate temperature control which in turn can lead to more precise operations in many industries and to energy savings.
2. Description of Related Art
Temperature control is widely used in operations ranging from industrial reactions to air conditioning to heating and refrigeration systems. Some operations require more precise control than others, although all such operations involve high-energy consumption and energy savings would be advantageous. The majority of systems rely on activation of the heat transfer system by a signal from the medium whose temperature is to be controlled and the response is to bring heat transfer elements into or out of operation depending upon the requirements of the medium. In many instances, the heat transfer element comprises a conduit through which a heat transfer fluid flows.
The disadvantage of the existing systems is that, outside of a limited operating range, the response of the system to temperature changes is coarse, it is often sluggish and has low resolution. This tends to result in bumpy irregular temperature profiles without the optimum degree of temperature control.
In an article in Collection Czechoslovak Chem. Comm. (Vol 47) (1982) pages 446 to 453 it is proposed to use a variable area cooling surface in which a retractable cooler was immersed into a reaction mixture. Introduction of the cooler into the reaction mixture could be used to increase the cooling effect and retraction from the mixture WOULD result in a decrease in the cooling effect. The article shows that this technique, to some extent, reduces the temperature surges and irregularities in the reaction mixture as it is cooled or heated. Achieving turbulence in the heat transfer fluid with this design is difficult, furthermore it requires complex apparatus to allow for movement of the cooling element whilst ensuring thermal insulation of the reaction vessel and preventing leaking of the reaction mixture.
U.S. Pat. No. 5,762,879 relates to a reaction heat control mechanism in which the heat exchange area is regulated. In U.S. Pat. No. 5,762,879 the regulation is achieved by varying the height of the heat transfer fluid in an external temperature control jacket which surrounds the reactor. Controlling the heat transfer area by this method requires a stable surface which is incompatible with the need to maintain high flows and high turbulence of heat transfer fluids. This leads to sluggish control response and reduced heat transfer capacity.
The quality of temperature control is dependant on how fast the temperature of the heat transfer surface can be raised and lowered. This in turn is dependant on the resistance to heat flow, the thermal gradient and how fast the heat transfer fluid can be delivered to the heat transfer surface.